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Motor-boat noise makes fish bad parents, leading to the death of their babies

22 June 2017

Noise from motorboats is making fish become bad parents, and reducing the chance of their young surviving, research led by marine experts at the Universities of Bristol and Exeter has shown.

The sound of motorboat engines disturbed coral reef fish so acutely it changed the behaviour of parents, and stopped male fish properly guarding their young, feeding and interacting with their offspring. The research, which involved playing recordings of natural reef noise or intermittent motorboat noise around 38 fish nests over 12 days, found that the death-rates of baby fish exposed to boat engine noise increased significantly, with six of the 19 boat-noise nests suffering complete mortality.

Dr Sophie Nedelec, University of Exeter, said: “Parental care behaviour seems to be impaired in noisy conditions and we believe this makes it easier for predators to strike their offspring. It is likely the parents were either stressed or distracted by the noise, giving an advantage to the predators in this case.” She added, “Parental care is widespread in the animal kingdom; from blue tits to blue whales, so there could be big implications for populations of animals affected by noise.”

Noise from boats is a global pollutant. Professor Andy Radford, University of Bristol, said: “Experiments that measure survival in natural conditions – as we have done in this study – are crucial if we are to understand fully the impact of anthropogenic noise.”

The researchers believe motorboat noise should be factored in when trying to protect fish stocks and manage fisheries. Dr Steve Simpson, an expert of the impact of noise on marine life at the University of Exeter, said: “This study raises important implications for managing the noise of the 100,000s of motorboats used around the world in coral reef environments. We are now considering acoustic quiet zones and corridors, and exploring how engine and propeller development can reduce the impact of this globally prevalent pollutant.”

The researchers predicted that their field research into the effect of man-made noise on coral fish could have wider implications for the survival of other marine species, and even birds and mammals. They called for more research in these areas. Noise from boats and has already been shown to affect the way fish, mammals, birds and invertebrates behave. It can force them to change their habitat to get away from the noise and reduce their success finding a mate. Boat noise can travel for many kilometres underwater.

Motorboat noise is the most common source of man-made noise in shallow reef environments. The scientists warned that, because they broadcast the motorboat engine noise through underwater loudspeakers which do not broadcast the full range of sounds produced by motorboats, their results could be conservative.

The males and female spiny chromis, a coral reef fish which lives in the tropical Western Pacific, bring up their offspring together, with males contributing more care than females of the species.Fish exposed to the motorboat noise spent far more time chasing and making aggressive strikes at other fish, compared to males exposed to recordings of ambient sound. The scientists believe this increase in aggressive behaviour may have been be due to ‘heightened stress’, or distraction by the noise which led to decision-making errors, so the fish attacked or chased fish that were not a predatory threat.

The research is published on June 7th in Proceedings of the Royal Society B Journal.

It was supported by a NERC Knowledge Exchange Fellowship, the UK Department for Environment, Food and Rural Affairs, the ARC Centre of Excellence for Coral Reef Studies, an EPSRC studentship and Subacoustech.